1. Field of the Invention
The present invention relates to an organic light emitting diode display device, and more particularly to an organic light emitting diode display device which may achieve a narrow bezel and enhance reliability.
2. Discussion of the Related Art
Image display devices to display various information on a screen are core technologies of the information age and are being developed to achieve thinner, lighter and higher performance portable designs. Organic light emitting diode display devices to display an image via control of light emission of an emission layer are getting the spotlight as flat panel display devices that may reduce disadvantageous weight and volume of a Cathode Ray Tube (CRT).
Such organic light emitting diode display devices include Organic Light Emitting Diodes (OLEDs) that are self-luminous using a thin emission layer between electrodes. A typical organic light emitting diode includes a first electrode that is an anode connected to a thin film transistor formed in each sub-pixel area, an Emission Layer (EML), and a second electrode that is a cathode.
The above-described organic light emitting diode forms excitons via recombination of holes and electrons in the emission layer when voltage is applied to the first and second electrodes, and light is emitted as the excitons return to the grounded state. A protective film is disposed on the organic light emitting diode to cover the organic light emitting diode and serves to prevent invasion of moisture and oxygen to the organic light emitting diode.
The organic light emitting diode is easily deteriorated by external factors, such as moisture, oxygen, ultraviolet light, device fabrication conditions, and the like. Therefore, in a typical organic light emitting diode display device, a substrate provided with organic light emitting diodes is bonded to an encapsulation substrate via an adhesive layer.
FIGS. 1A and 1B are sectional views of a typical organic light emitting diode display device which is of a bottom emission type. FIG. 2 is a photograph of an edge of a typical encapsulation substrate.
As exemplarily shown in FIG. 1A, a typical organic light emitting diode display device includes a substrate, an organic light emitting diode array 10 that includes thin film transistors arranged on the substrate and organic light emitting diodes connected to the thin film transistors, an encapsulation substrate 20 configured to cover the organic light emitting diode array 10, and a polarizer 40 attached to a bottom surface of the organic light emitting diode array 10. In addition, a border 50 is provided to surround edges of the organic light emitting diode array 10, the encapsulation substrate 20, and the polarizer 40.
In particular, in the case of an organic light emitting diode display device having a Chip On Film (COF) structure, a film 30a on which a drive chip 30b to drive the organic light emitting diode array 10 is mounted is connected to a pad 10a of the organic light emitting diode array 10. To enhance adhesion between the pad 10a and the film 30a, however, the film 30a needs be folded once. Accordingly, in this case, a sufficient distance D between the border 50 and the organic light emitting diode array 10 is needed, which makes it impossible to achieve a narrow bezel.
As exemplarily shown in FIG. 1B, such a narrow bezel may be achieved if the film 30a is configured to directly extend to the encapsulation substrate 20. However, cracks or disconnection of the film 30a may occur due to an edge of the encapsulation substrate 20 as exemplarily shown in FIG. 2. In addition, although providing the film 30a with a buffer may prevent damage to the film 30a, this may increase a thickness of the film 30a. Therefore, it is necessary to consider a width of the pad 10a and a design margin between the pad 10a and the encapsulation substrate 20.